Load bank

ABSTRACT

A system and method is disclosed for creating and/or maintaining an electrical load on a diesel engine generator for use on a marine vessel in order to avoid the harmful effects of no-load or low-load operation of the diesel engine. The parasitic load bank system  10  utilizes the heat transfer fluid  23  contained in the closed circulation loop  28  of a chille7d-fluid air conditioning system  14  for creating and/or maintaining the electrical load on the diesel engine generator  12  by utilizing a load bank controller  44  for diverting a portion  23   c  of the heat transfer fluid  23   a  being supplied to the vessel&#39;s air handlers  42  into heat exchange relationship with the heat transfer fluid  20   b  discharged from the air conditioning system&#39;s source of heat transfer  18  such that the heat exchanged heat transfer fluid  23   f  activates the source of heat transfer  18 , which may be a chiller, reverse-cycle chiller or heat pump, to create an electrical power demand on the diesel engine generator  12.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a load bank for diesel engines and moreparticularly to a system, apparatus and method that modifies andutilizes a chilled-fluid air conditioning system onboard a marine vesselfor creating and/or maintaining an electrical load on one or more dieselengine-powered generators to avoid the deleterious and/or damagingeffects of low-load or no-load operation for the diesel engine.

2. Background of the Invention

Marine diesel engine generators are designed for operation atpredetermined temperatures and pressures that can only be achieved whenthe diesel engine powering the generator is operated under load,generally sixty percent of the engine's rated load capacity or greater.The operation of a diesel engine generator at low loads, particularlyover a long period of time, can lead to undesirable consequences, amongwhich are incomplete combustion of the diesel fuel resulting in fouledfuel injectors and valves; condensation formation within the enginewhich can cause the various parts of the internal engine to corrode andcan also lead to a breakdown or degradation of the engine's lubricatingoil; condensation of exhaust within the engine's exhaust stacks,commonly referred to as “wet stacking,” as well as condensation in themanifolds thereby causing system corrosion and valve damage; systemcarbon buildup in the exhaust system resulting in the risk of an exhaustsystem fire; improper seating of the engine's gaskets and sealsresulting in oil leaks; and improper seating of the engine's pistonrings which will ultimately be responsible for excessive oil consumptionand shortened piston and ring longevity thereby leading to reduced horsepower for the engine. The foregoing effects of low load operation arecumulative over a period of time.

Load demands on diesel engine generators, particularly those used inmarine operations onboard a seafaring vessel, are generally created bythe vessel's electrical requirements. Marine engine generators aretherefore designed and sized for the maximum anticipated load forproviding electrical power to operate the vessel's air conditioning,pumps, motors, galley requirements, and appliances, etc., in the eventthat all of the vessel's electrical apparatus is on-line at any point intime.

One of the more varying electrical power demands onboard a seafaringvessel, and a common source for low-load engine operation, is created bythe vessel's air conditioning system due to the substantial electricalrequirements and the fluctuating conditions of the weather. The majorityof larger marine vessels, such as yachts, utilize conventionalfluid-chilled air conditioning systems to heat and cool the vessel ascircumstances warrant. In the cooling mode, these systems employ acirculating heat transfer fluid for removing heat from variouscompartments and staterooms of the vessel. As shown in FIG. 1, the heattransfer fluid 23, typically fresh water, is pumped through a closedcirculation loop 28 that extends through one or more sources of heattransfer, typically one or more chillers or reverse-cycle chillersrepresented by diagram box 18, for ultimately exchanging its heat withseawater 21 transported through the chiller(s) by the action of seawaterpump 19. Once sufficiently cooled, the heat transfer fluid 23 iscirculated to one or more air handlers (represented by diagram box 42)distributed throughout various locations of the vessel for absorbing theheat from the air in the vessel's compartments. The heat-absorbed returnheat transfer fluid 23 is then circulated back to the chiller(s) by theaction of circulating pump 24 where it is cooled once again to completethe air conditioning cycle. The power for operating the chiller(s),pumps and other electrical apparatus in the air conditioning system isderived from diesel engine generator 12 when the vessel is at sea.

The conventional chiller, an example of which is described andillustrated in U.S. Pat. No. 4,926,649, comprises an evaporator incombination with a compressor and condenser for cooling the heattransfer fluid contained within the closed circulation loop. Inapplications for use onboard marine vessels, electrical power issupplied to the compressor by the diesel engine generator for drawinglow pressure refrigerant gas from an evaporator, compressing it, andthen discharging it in a higher pressurized gaseous state to acondenser. The condenser in turn condenses the hot gaseous refrigerantinto a liquid by transmitting its heat to a second heat transfer fluid,typically seawater, pumped through the condenser. As the sea water ispumped through the chiller condenser, it absorbs the heat from the hotgaseous refrigerant and is returned back to the sea.

In the heating mode, i.e., when it is desired to supply heat to thecirculating heat transfer fluid, a reversing valve is employed in thechiller for reversing the flow of refrigerant to the chiller's condenserin order to absorb heat from the sea water and transfer it to thecirculating heat transfer fluid. In this mode of operation, the chilleracts as a heat pump and is referred to as a reverse-cycle chiller. Aconventional heat pump may also be utilized, particularly when thevessel is relegated to cold climate operations.

As an example, a one hundred foot vessel may employ four 5-ton chillersto satisfy the air conditioning needs of the vessel's compartments.During the summer daytime hours, the heat load for the vessel will besufficient to require that all of the four chillers be online. Theelectrical power demand for the operation of the chillers will create asufficient load on the diesel engine generator(s) thereby more thansatisfying the minimum load requirements for the generator(s). Aftersunset, however, the climate air temperature will drop and the heat loadof the vessel will be substantially reduced. As the weather cools, thechillers will begin to stage off one by one, and only one of the fourchillers will probably be needed to satisfy the vessel's cooling needs.It is during this time that the diesel engine which powers thegenerator(s) will be operating under very low-load conditions.

The situation is reversed when the vessel is navigating through a coolerclimate or operating in cool-climate conditions. During the eveninghours, the heating demand for the vessel will be sufficient to requirethat all four reverse-cycle chillers be online. Alternatively, resistantin-line water heaters may be employed in lieu of the reverse-cyclechillers. In any evert, their activation will require electrical powerfor the operation of all the reverse-cycle chillers (or in-lineresistant water heaters, as the case may be), and the minimum requiredload on the diesel engine will be more than satisfied. After sunrise,however, the air temperature will increase and the heating demand forthe vessel will be reduced. As the weather temperature increases, thereverse-cycle chillers will stage off one by one, and only one or two ofthe four chillers will probably be needed to maintain the vessel'sheating needs. Once again, the engine generator(s) will be operatingunder low-load conditions.

3. The Related Art

An example of a refrigeration apparatus powered by a diesel enginegenerator is described in U.S. Pat. No. 5,584,185, issued to Rumble etal. on Dec. 17, 1996. The refrigeration apparatus comprises acompressor, a water-cooled condenser, a chiller/evaporator and apositive displacement circulating pump, all of which are arranged inheat exchange relationship with a recirculating coolant circuit. Theengine and refrigeration apparatus utilize an electronic control systemthat senses when electrical power is required or when the coolanttemperature rises above a datum level so as to initiate a prescribedstart sequence for the engine, and further, will automatically shut downthe engine when a no-load is sensed for the engine. In the lattercircumstance, the engine will remain on standby awaiting a power demand.

Multiple chilled-fluid producers are also disclosed in U.S. Pat. No.6,240,867 B1, issued to Hoyle et al. on Jun. 5, 2001. The patentdiscloses their distribution within a watertight zone of amultiple-zoned naval ship for independent operation to avoid or reducethe risk of the vessel's functioning capability when impacted by amissile or torpedo. The chilled fluid producers disclosed may alsorequire a flow of water, either sea or fresh water, into which heat canbe rejected. U.S. Pat. No. 4,926,649 issued to Martinez, Jr. on May 22,1990 also discloses the use of multiple chillers to cool a commercialbuilding in a way that utilizes less energy by turning off one or moreof the multiple chillers, and also by varying the total water flowthrough the chillers.

Various controllers for operating multiple chillers are also disclosedin the patent literature. For example, in U.S. Pat. No. 4,506,516 issuedto Lord on Mar. 26, 1985, the use of a microprocessor is disclosed foroperating multiple chillers, and in U.S. Pat. No. 4,463,574 issued toSpethmann et al. on Aug. 7, 1984, a controller is disclosed foroptimally selecting a combination of chillers having dissimilarefficiency characteristics to efficiently meet a building's airconditioning load. Electric controller systems for efficiently operatingair conditioning systems are also known, as for example in U.S. Pat. No.4,147,296, issued to Spethmann on Apr. 3, 1979, which discloses anelectric controller system for reducing and/or limiting a building'selectrical power consumption by a proportional amount in order toprevent the power consumption from exceeding a predetermined demandlimit; and in U.S. Pat. No. 5,946,926 issued to Hartman on Sep. 7, 1999,wherein a single-circuit, chilled fluid cooling system incorporates avariable flow chilled water distribution system to obtain stableoperation at reduced variable flow rates of the circulating chilledfluid.

Finally, various approaches have been taken to compensate for low-loadoperation of a diesel engine generator onboard marine vessels. Forexample, load banks have been formulated whereby resistive load elementsin the form of heating coils are inserted into a separately fabricatedintake line coupled with a seawater pump to receive and dischargeseawater from and to the vessel. Heating the seawater in this mannerdemands electrical power from the generator which in turn creates a loadon the diesel engine powering the generator. In addition to requiringadded space onboard the vessel, and the associated costs for assemblingand incorporating the load bank into the vessel, the coils used to heatthe seawater encounter calcification over a period of time due to theseawater's high mineral content. This results in the coils being coatedwith calcium and other minerals that quickly leads to the inability ofthe coils to transmit heat to the seawater. Consequently, the calcifiedcoils become an added maintenance item in that they must be descaled byrepeated acid washing, or simply replaced. Load banks utilizing thismethod of operation are available from a variety of sources, one ofwhich is Simplx, Inc. of Springfield, Ill.

SUMMARY OF THE INVENTION

In accordance with a broader aspect of the invention, a system,apparatus and method is provided for maintaining an electrical load on amarine diesel engine generator utilizing the heat transfer fluidcontained within the closed fluid circulation loop of marine vessel'schilled fluid air conditioning system. More specifically, a system isprovided that comprises a closed-loop fluid air conditioning system forexchanging heat with the air in the vessel, comprising a first heattransfer means, e.g., one or more sources of heat transfer thatcomprises a chiller, reverse-cycle chiller or heat pump, preferably aplurality arranged in parallel relationship relative to each other, thatreceives therein and discharges therefrom a first heat transfer fluid,typically seawater, for ultimately exchanging heat with a second heattransfer fluid, generally water, a mixture of water and propyleneglycol, or a mixture of water and ethylene glycol, the glycol componentbeing present in an amount of from about 5 to about 25 percent by volumebased on the total volume of the mixture. The second heat transfer fluidis supplied to and returned from the vessel within a closed circulationloop for exchanging heat with the air in the vessel.

The system additionally comprises a load bank comprising (i) controllermeans for diverting at least a portion of the second heat transfer fluidbeing supplied to the vessel, into heat exchange relationship with athird heat transfer fluid; and (ii) second heat transfer means, e.g., aheat exchanger, for exchanging heat between the diverted second heattransfer fluid and the third heat transfer fluid.

In a preferred embodiment of the invention, the third heat transferfluid is the first heat transfer fluid in the form of seawaterdischarged from the first heat transfer means. Thus, the first heattransfer fluid will generally comprise seawater, although in anotherembodiment of the invention, the first heat transfer fluid will compriseseawater; and the third heat transfer fluid will comprise seawaterprovided to the second heat transfer means or heat exchangerindependently of the seawater being received by the source of heattransfer.

Once heat-exchanged, the diverted second heat transfer fluid is returnedto the first heat transfer means for activation thereof to create anelectrical power demand on the diesel engine generator.

In another preferred embodiment of the invention, the diversion by thecontroller means of the portion of second heat transfer fluid beingsupplied to the vessel, is undertaken in response to a predeterminedtemperature value of the returning second heat transfer fluid, i.e., thesecond heat transfer fluid returning from the vessel after it hasexchanged heat with the air in the vessel. In order to accomplish this,and in accordance with yet another embodiment of the invention, thecontroller means comprises at least one valve for admitting the divertedportion of second heat transfer fluid supply therethrough. In order tofacilitate the diversion, it is preferential that the valve be operablycoupled with a thermostat that is in temperature sensing relationshipwith the returning second heat transfer fluid. A plurality of valves andcorresponding thermostats making up the controller means allows varyingamounts of the second heat transfer fluid to be diverted to the secondheat transfer means, e.g., a heat exchanger. Each of the valves ispreferably operated in response to a thermostat setting reflective ofthe temperature of the returning second heat transfer fluid. As afurther embodiment, each of the thermostats is in temperature sensingrelationship with the returning second heat transfer fluid such thateach of the valves is operated in response to a signal generated by itscorresponding thermostat reflective of a predetermined temperature ofthe returning second heat transfer fluid detected upstream of itscorresponding valve.

While not intending to exclude variations or other types, the heatexchanger may be of the plate, shell and tube, or tube and tube typeheat exchanger, the plate type heat exchanger being preferred due to itsrelatively minimal space occupancy when incorporated into the system.

When the closed-loop fluid air conditioning system is used to cool theair in the vessel compartments, the source of heat transfer takes theform of either a chiller or reverse-cycle chiller. In larger vessels, aplurality of chillers or reverse-cycle chillers, or combinationsthereof, are generally utilized, the chillers and/or reverse-cyclechillers being arranged in parallel relationship relative to each other.In order to assist in the heating of the returning second heat transferfluid, the system may optionally comprise, in addition to the secondheat transfer means or heat exchanger, one or more electrical resistantfluid heating devices in communication with the returning second heattransfer fluid for transferring heat thereto. The fluid heating deviceis preferably in the form of one or more electrically operated resistantwater heaters, preferably a plurality arranged in parallel relationshiprelative to each other.

In another embodiment of the invention, and as an alternative to the useof a heat exchanger and valves for heating a diverted portion of thesecond heat transfer fluid when the closed-loop chilled fluid airconditioning system is used to cool the vessel air, the load bank maycomprise a fluid heating means comprising one or more electricalresistant fluid heating devices operably coupled with a controller meansfor heating the second heat transfer fluid returning from the vessel tothe source(s) of heat transfer in response to a predeterminedtemperature of the returning heat transfer fluid detected upstream ofthe fluid heating means. The fluid heating means comprises at least oneelectrically operated resistant water heater powered by the dieselengine generator. The controller means comprises at least one thermostatin temperature sensing relationship with the returning second heattransfer fluid. The load bank preferably comprises a plurality ofelectrically operated resistant water heaters, arranged in parallelrelationship relative to each other, each water heater being powered bythe diesel engine generator and operably coupled with and controlled bya corresponding thermostat in response to a thermostat settingreflective of a predetermined temperature of the returning second heattransfer fluid detected upstream of its corresponding water heater.

When the closed-loop fluid air conditioning system is used to heat theair in the vessel compartments, the source of heat transfer will takethe form of either a reverse-cycle chiller or heat pump, preferably aplurality of reverse-cycle chillers or heat pumps, or combinationsthereof, arranged in parallel relationship relative to each other. Whenthe vessel is operating in very cold climate conditions, it will beappreciated that additional sources of heat may be required to heat thecirculating second heat transfer fluid for supplying an adequate amountof heat to the vessel compartments. Therefore, in addition to thesource(s) of heat transfer, the system may optionally comprise one ormore electrical resistant fluid heating devices, powered by the dieselengine generator and preferably in the form of an electrically operatedresistant water heater, in communication with the second heat transferfluid being supplied to the vessel for heating the same.

Another embodiment of the invention includes a load bank for a marinediesel engine generator electrically coupled with a source of heattransfer in a closed-loop fluid air conditioning system that receivesand discharges a primary heat transfer fluid for ultimately exchangingheat with a secondary heat transfer fluid, the secondary heat transferfluid being supplied to and returned from the compartments of a marinevessel within a closed circulation loop for exchanging heat with the airin the vessel compartments, comprising (a) controller means fordiverting at least a portion of the secondary heat transfer fluid supplyinto heat exchange relationship with a tertiary heat transfer fluid; and(b) a heat exchanger for exchanging heat between the diverted secondaryheat transfer fluid and the tertiary heat transfer fluid; whereby thediverted, heat-exchanged, secondary heat transfer fluid is returned tothe source of heat transfer for activation thereof to create anelectrical power demand on the diesel engine generator for maintaining aload thereon. The primary, secondary and tertiary heat transfer fluidscorrespond respectively with the first, second and third heat transferfluids of the system described above and include the various embodimentsset forth for the first, second and third heat transfer fluids as partof the present load bank.

The controller means of the load bank comprises at least one valve whichis usually operably coupled with a thermostat that is in temperaturesensing relationship with the returning secondary heat transfer fluidfrom the vessel. When coupled with the thermostat, the valve is operatedin response to a signal generated by the thermostat reflective of apredetermined temperature of the returning secondary heat transfer fluiddetected upstream of the valve. In another embodiment, the load bankcontroller means comprises a plurality of valves and correspondingthermostats, the valves being arranged in parallel relationship relativeto each other. As with the heat exchanger described for the systemabove, the heat exchanger of the load bank may be a plate type heatexchanger, a shell and tube type heat exchanger or a tube and tube typeheat exchanger.

It will be understood that the closed-loop fluid air conditioning systemaccording to the invention is not restricted to the use of a chiller,reverse-cycle chiller or heat pump for heating and/or cooling thecirculating heat transfer fluid contained within the closed circulationloop. Instead, the closed-loop air conditioning system forming part ofthe system for maintaining an electrical load on a diesel enginegenerator for use on a marine vessel, may comprise (a) a fluid heatingmeans, powered by the diesel engine generator, comprising at least oneelectrical resistant fluid heating device for heating a first heattransfer fluid being supplied to and returned from the vessel within aclosed circulation loop for heating the air in the vessel. In this case,the first heat transfer fluid is the circulating heat transfer fluidcontained within the closed circulation loop. The system for maintainingan electrical load on a diesel engine generator also comprises (b) aload bank comprising (i) controller means for diverting at least aportion of the first heat transfer fluid being supplied to the vessel,into heat exchange relationship with a second heat transfer fluid; and(ii) a heat exchanger for exchanging heat between the second heattransfer fluid and the diverted portion of the first heat transfer fluidwhereby the heat-exchanged, diverted first heat transfer fluid isreturned to the fluid heating means for activation thereof to create anelectrical power demand on the diesel engine generator for maintaining aload thereon.

The first heat transfer fluid or circulating heat transfer fluid maycomprise water, a mixture of ethylene glycol and water, or a mixture ofpropylene glycol and water, the glycols being present in theirrespective mixtures in an amount of from about 5 percent to 25 percentbased on the total volume of the mixture. The second heat transfer willgenerally comprise seawater.

In this embodiment of the invention, the fluid heating means comprisesat least one electrically operated resistant water heater, preferably aplurality arranged in parallel relationship relative to each other.

It is understood that the controller means and heat exchanger of theload bank for this embodiment of the invention correspond with thecontroller means and heat exchanger described hereinbefore. They alsoinclude the various embodiments of the previously described controllermeans and heat exchanger of the load bank associated with the use of achiller, reverse-cycle chiller or heat pump as part of the closed-loopfluid air conditioning system.

The invention also encompasses a method for maintaining a load on thediesel engine generator onboard a marine vessel utilizing thecirculating heat transfer fluid contained within the closed circulationloop of a fluid air conditioning system to exchange heat with the air inthe vessel, comprising (a) transporting a primary heat transfer fluidthrough a first heat transfer means of the closed circulation loop fluidair conditioning system for ultimately exchanging heat with thecirculating heat transfer fluid; (b) supplying and returning thecirculating heat transfer fluid in the closed circulation loop to andfrom the vessel, respectively, for heat exchange with the air therein;(c) diverting at least a portion of the circulating heat transfer fluidbeing supplied to the vessel, into heat exchange relationship with atertiary heat transfer fluid; and (d) returning the diverted,heat-exchanged circulating heat transfer fluid to the first heattransfer means whereby the first heat transfer means is activated tocreate an electrical power demand on the diesel engine generator formaintaining a load thereon. In accordance with the method, the firstheat transfer means may comprise a chiller, reverse-cycle chiller orheat pump, preferably a plurality of chillers, reverse-cycle chillers orheat pumps, or combinations thereof, arranged in parallel relationshiprelative to each other.

The portion of circulating heat transfer fluid being supplied to thevessel is preferably diverted in response to a predetermined temperaturevalue of the returning primary heat transfer fluid, usually by acontroller means comprising at least one valve. As a preference, thevalve is operably coupled with a thermostat that is in temperaturesensing relationship with the returning circulating heat transfer fluid,the valve being operated in response to a thermostat setting reflectiveof the temperature of the returning circulating heat transfer fluidwhich is detected upstream of the valve. In order to more effectivelycontrol the actuation of the sources of heat transfer, the controllermeans will generally comprise a plurality of valves and correspondingthermostats, the valves being arranged in parallel relationship relativeto each other.

The heat exchange of the diverted portion of circulating heat transferfluid and primary heat transfer fluid is generally undertaken by asecond heat transfer means comprising a heat exchanger which may be aplate type heat exchanger, a shell and tube type heat exchanger, or atube and tube type heat exchanger.

The primary and tertiary heat transfer fluids correspond respectivelywith the first and third heat transfer fluids of the system describedabove and include the various embodiments set forth for the first andthird heat transfer fluids as part of the present method. Thecirculating heat transfer fluid may comprise water, a mixture ofethylene glycol and water, or a mixture of propylene glycol and water,the glycol component being present in its respective mixture in anamount of from about 5 to 25 percent based on the total volume of themixture.

Also encompassed by the invention is a method for maintaining a load ona diesel engine generator onboard a marine vessel utilizing thecirculating heat transfer fluid contained within the closed circulationloop of a chilled-fluid air conditioning system comprising at least onechiller or reverse-cycle chiller, the method comprising (a) supplyingand returning the heat transfer fluid in the closed circulation loop toand from the vessel, respectively, for cooling the air therein; (b)heating the heat transfer fluid returning from the vessel to the chilleror reverse-cycle chiller; and (c) returning the heated heat transferfluid to the chiller or reverse-cycle chiller for activating the same tocreate an electrical power demand on the diesel engine generator formaintaining a load thereon. The heat transfer fluid is preferably heatedwith at least one electrical resistant fluid heating device such as anelectrically operated resistant water heater, preferably in response toa predetermined temperature value of the returning heat transfer fluid.The operation of the fluid heating device is desirably controlled by athermostat in temperature sensing relationship with the returning heattransfer fluid upstream of the fluid heating device. In order to controlthe temperature of the returning heat transfer fluid for activating thechiller or reverse-cycle chiller, it is preferred that the returningheat transfer fluid be heated by a plurality of resistant water heaters,each water heater being operably controlled by a correspondingthermostat in response to a thermostat setting reflective of apredetermined temperature of the returning heat transfer fluid detectedupstream of the resistant water heaters.

BRIEF DESCRIPTION OF THE DRAWINGS

A complete understanding of the invention may be obtained by referenceto the following specification when taken in conjunction with theaccompanying drawings wherein certain preferred embodiments areillustrated and wherein like numerals refer to like parts throughout.Thus,

FIG. 1 is a block diagram of a conventional, closed loop, chilled waterair conditioning system used onboard a marine vessel.

FIG. 2 is a block diagram of a combined closed loop, fluid airconditioning system and load bank for use onboard a marine vessel inaccordance with one embodiment of the invention.

FIG. 3 is a schematic diagram of a combined closed loop, fluid airconditioning system and load bank for use onboard a marine vessel inaccordance with another embodiment of the invention.

FIG. 4 is a schematic diagram of a combined closed loop, chilled waterair conditioning system and load bank for use onboard a marine vessel inaccordance with yet another embodiment of the invention.

FIG. 5 is a schematic diagram of the load bank heat exchanger 46 shownin FIG. 3 in accordance with another embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF

The present invention provides a system, apparatus and method forcreating and maintaining an electrical load on a marine diesel enginegenerator of a seafaring vessel utilizing the vessel's closed loop,fluid air conditioning system. The present system takes advantage of anexisting network already in place onboard seafaring vessels with minormodifications to the network's structure for implementing and creatingan electrical power load for a marine diesel engine generator.Substantial economical costs are derived from the invention over thoseapparatus and systems that employ separate load banks.

Referring now to FIG. 2, there is shown for illustrative purposes only,a block diagram representing, in one embodiment of the invention, asystem 10 for creating and/or maintaining an electrical load on a marinediesel engine generator 12 utilizing an integrated closed loop fluid airconditioning system 14 and a load bank 16. More specifically, a dieselengine-powered generator 12 is provided for supplying electrical powerto a closed loop, fluid air conditioning system 14. Air conditioningsystem 14 comprises at least one source of heat transfer 18 in the formof, for example, a chiller, reverse-cycle chiller or heat pump, thatreceives and discharges a first heat transfer fluid 20, typicallyseawater. For the purposes of this invention, the term “source of heattransfer” is used as a generic term for describing a chiller,reverse-cycle chiller and/or a heat pump as those devices are known inthe air conditioning industry. First heat transfer fluid 20 is arrangedin heat exchange relationship with a second heat transfer fluid 23,which is generally fresh water, for ultimately exchanging heat betweenthe seawater and fresh water. Second heat transfer fluid 23 istransported from the source of heat transfer 18 by means of pump 24 toone or more air handlers located in the various compartments of thevessel (represented by diagram box 42), and returned back to the sourceof heat transfer 18 within a closed circulation loop 28 after exchangingheat with the air in the vessel compartments.

System 10 additionally comprises a load bank 16 that includes acontroller 44 for diverting a portion 23 c of the second heat transferfluid 23 into heat exchange relationship with the first heat transferfluid 20 b discharged from the source of heat transfer 18, preferably inresponse to a predetermined temperature value of the returning secondheat transfer fluid 23 b exiting air handlers 42. Heat exchange betweenthe first and second heat transfer fluids 20 b and 23 c, respectively,is undertaken by heat exchanger 46. When the diverted heat-exchangedsecond heat transfer fluid 22 d, combined with the remaining heattransfer fluid 23 b exiting air handlers 42 (the combination of the twobeing represented by reference numeral 23 e) is returned to circulatingpump 24 and introduced once again to the source of heat transfer 18, thesource of heat transfer is activated in response to a demand fortemperature-conditioned air in the vessel compartments. Thus, whenactivated, the source of heat transfer will exchange heat with theincoming second heat transfer fluid 23 f to satisfy the air temperatureconditions required by the vessel's compartments. As a result, anelectrical power demand is placed on generator 12 for operating thesource of heat transfer 18. The additional load placed on generator 12by load bank 16 creates a means whereby a load on the diesel engine,utilizing the closed loop heat transfer fluid of the vessel's airconditioning system, can be assured to avoid low-load or no-loadoperation of the engine.

Referring now to FIG. 3, and in accordance with another embodiment ofthe invention, the system illustrated in FIG. 2 is augmented in that theair conditioning system 14 comprises a plurality of sources of heattransfer 34,35,36,37 (referred to hereinafter as “heat transfersources”) arranged in parallel relationship relative to each other, eachof which is configured to receive a first heat transfer fluid 20 in theform of seawater 21 via the action of seawater pump 19. For purposes ofdescribing the invention, it will be understood that each of referencenumerals 34,35,36,37 can represent and include chillers, reverse-cyclechillers, or heat pumps, or combinations thereof, depending on whetherthe air conditioning system is being used to cool or heat the vesselair. Accordingly, when cooling of the vessel is required, the source ofheat transfer can include a chiller or reverse-cycle chiller, the formerbeing provided with a reversing valve (not shown) for transforming thechiller into a reverse-cycle chiller which has the dual capability ofacting as a chiller or heat pump. And when heating of the vessel air isnecessitated, the source of heat transfer may include a reverse-cyclechiller or heat pump.

The seawater 21 a pumped to and from heat transfer sources 34,35,36,37by the action of seawater pump 19 via inlet conduit 6 and dischargeconduit 8, is arranged in heat exchange relationship with a refrigerantwithin the heat transfer sources for ultimately exchanging heat with thesecond heat transfer fluid 23 by means of a condenser, evaporator andcompressor (not shown) as is well known in the air conditioning art. Thesecond heat transfer fluid 23, which is typically in the form ofcirculating water 23 f, is transported through the heat transfer sourcesby circulating pump 24. In this manner, heat transfer sources34,35,36,37 of air conditioning system 14 are capable of supplying achilled or heated circulating fluid 23 to closed circulation loop 28,depending on whether cooling or heating of the vessel is required.

As further illustrated in FIG. 3, circulating water 23 is supplied tocirculation loop 28 from a fresh water supply 22 through expansion tank25. Fresh water supply 22 also serves the function of replenishing thewater in circulation loop 28 when, for example, moisture loss occurs,e.g., due to water leakages in the closed loop system, etc.

It will be understood that the second heat transfer fluid, in additionto water, may also comprise the inclusion of other additives, inparticular a mixture of ethylene glycol and water, or a mixture ofpropylene glycol and water, the glycol component being present in itsrespective mixture in an amount of from about 5 percent to about 25percent, based on the total volume of the mixture. When water is used asthe second heat transfer fluid, it usually has the glycol componentadded to it for a variety of reasons, chief among them being that theethylene or propylene glycol acts as a lubricant for the internal movingcomponents that the closed circulation loop 28 comes in contact with.The glycol component also serves as a safeguard for the chiller,reverse-cycle chiller and heat pump to prevent them from freezing upduring cold climate operating conditions.

Once heated or cooled by any or all of heat transfer sources34,35,36,37, circulating water 23 a is pumped and distributed, viaconduit 28 a, to the various compartments of the vessel by means of, forexample, an arrangement of air handlers represented by reference numeral42, the details of which are commonly known in the air conditioningindustry and are therefore not illustrated herein. After being suppliedto air handlers 42, the heated or chilled circulating water 23 a istransported to each of the vessel compartments which contain a series ofcoils equipped with motor driven fans (not shown) for exchanging heatwith the respective compartment air and circulating water 23 a. Theheat-exchanged circulating water 23 b is then transported back to heattransfer sources 34, 35, 36, 37 via the action of pump 24 where it iscooled or heated once again to complete a continuous air conditioningcycle.

In order to create and/or maintain an electrical load on generator 12utilizing the vessel's air conditioning system 14 illustrated in FIGS. 2and 3, system 10 includes a load bank 16 that comprises, in oneembodiment of the invention, a controller means in the form of, forexample, load bank controller 44 and a load bank heat transfer means inthe form of heat exchanger 46. Controller 44 comprises a means fordiverting the circulating water, for example, at least one water valve,preferably a plurality of valves (designated by reference numerals48,49,50,51), for admitting therethrough a portion of the pressurizedcirculating water 23 a being supplied to air handlers 42. The divertedportion of circulating water, indicated by the direction of arrows inFIG. 3, is represented by reference numeral 23 c. Once any or all ofvalves 48,49,50,51 are opened, circulating water 23 c is transportedthrough conduit 28 b to load bank heat exchanger 46 by the action ofcirculating pump 24. As the circulating water 23 c enters heat exchanger46, it is subjected to heat exchange with the seawater 21 b exiting anyor all of heat transfer sources 34,35,36,37 via conduit 8 a. Afterexchanging heat with circulating water 23 c, the seawater 21 c exitingheat exchanger 46 is returned to the sea 21 via conduit 8 b.

It will be understood that the load bank is not restricted to the soleuse of seawater 21 b exiting any one or all of heat transfer sources34,35,36,37 for exchanging heat with circulating water 23 c. Heatexchanger 46 can receive and discharge a heat exchange fluid from othersources, for example seawater directly from the sea. As shown in FIG. 5,this is accomplished by providing a separate seawater pump 27 that drawsseawater 21 from the sea via conduit 8 c through strainer 31 intoconduit 8 a disposed between pump 31 and heat exchanger 46. As seawater21 is pumped through heat exchanger 46, heat is exchanged withcirculating water 23 c entering the heat exchanger.

The heat-exchanged circulating water exiting heat exchanger 46,designated by reference numeral 23 d, is returned to closed circulationloop 28 via conduit 28 c and combined with the remainder of circulatingwater 23 b exiting air handlers 42. The combined circulating water 23 eis then fed to circulating pump 24 and transported as circulating water23 f to any or all of heat transfer sources 34,35,36,37 under the actionof circulating pump 24. Once received into the respective heat transfersources 34,35,36,37, the heat transfer sources are activated therebycreating an electrical power demand on generator 12. The diversion of aportion of the circulating water being supplied to air handlers 42, intoheat exchange with the seawater 8 b exiting heat transfer sources34,35,36,37, therefore acts as a load bank for creating an electricalpower demand on generator 12 which in turn relieves low-load or no-loadoperation of the diesel engine.

Any conventional type of heat exchanger can be used for exchanging heatbetween circulating water 23 c and seawater 21 b depending on a varietyof factors, primarily space availability onboard the vessel. Otherfactors include cost, design, and the materials making up the heatexchanger. While the invention is not deemed to be restricted to anyparticular kind of heat exchange apparatus, plate frame, tube-in-tubeand shell-and-tube are examples of heat exchangers that can be used. Aplate frame heat exchanger is preferred because it satisfies the economyof space requirement usually prevalent onboard marine vessels.

The diversion of circulating water 23 c to heat exchanger 46 can beundertaken by any conventional means. For example, the diversion ofcirculating water 23 c through any or all of valves 48,49,50,51 may beaccomplished by manually operating the valves under circumstances whenthe diesel engine is experiencing low-load or no-load conditions. Theoperation of the valve(s), however, is preferably undertakenautomatically, for example, by coupling each of the valves with anelectric motor (not shown) to open and close the valve for admitting ordenying water therethrough. In the air conditioning industry, thesetypes of valves are referred to as motorized water valves whichgenerally employ an electric motor for actuating a lever on the valvethat in turn displaces a plunger from a seat overlying a port within thevalve. When the lever is actuated by the electric motor and the plungerlifted, water will be admitted through the valve. The electric motor iscapable of reversing the lever for the return of the plunger to its seatthereby denying water flow through the valve. Other means forautomatically diverting a portion of circulating water 23 a from itsclosed circulating loop 28 include, but are not limited to,electrically, pneumatically or hydraulically operated solenoid valvesand any other valves commonly employed in the air conditioning industryfor passing fluids therethrough.

Each of valves 48,49,50,51 is electrically coupled with, via theircorresponding electric motors (not shown), temperature control means inthe form of thermostats 56,57,58,59, respectively, the thermostats beingcapable of sensing the temperature of the returning circulating water 23b from the vessel's air handlers 42 with temperature sensing devices 56t,57 t,58 t,59 t. In the embodiment illustrated in FIG. 3, thetemperature sensing devices are located at a point where the returningcirculating water 23 b leaves air handlers 42, but generally may belocated at any point in circulation loop 28 between air handlers 42 andload bank controller 44. Thermostats 56,57,58,59 are also capable ofgenerating and transferring an electrical signal to their respectiveelectric motors reflective of a predetermined temperature setting forthe returning circulating water 23 b. Once the signal from any one ofthermostats 56,57,58,59 is received by its corresponding electric motor,corresponding valves 48,49,50,51 are either opened or closed dependingon the temperature setting programed into the corresponding valve'sthermostat. For example, as shown in FIG. 3, if valve 48 is opened,circulating water 23 c is diverted from circulating water 23 a intoconduit 28 b of circulation loop 28 before circulating water 23 a entersthe vessel compartment air handlers 42. In similar fashion, therespective valve will close when the temperature of the returningcirculating water 23 b matches the temperature setting programed intothe corresponding thermostat for generating and transmitting anelectrical signal to the motorized valve for closing the valve.

Operation of system 10 for maintaining an electrical load on marinediesel engine generator 12 when the air conditioning system 14 is usedto cool the marine vessel will now be described. When the seafaringvessel is operating under warm weather conditions, the daytimetemperatures will be such that all of heat transfer sources 36,37,38,39of the air conditioning system will be online to cool the variouscompartments of the vessel. In this example, heat transfer sources36,37,38,39 will necessarily take the form of chillers or reverse-cyclechillers, or combinations thereof, and in the following description,will be collectively referred to as “chillers.”

Chillers 36,37,38,39 are operated by having seawater 21 transported tothem via conduit 6 by the action of seawater pump 19, and aftercirculating through the chillers, seawater 21 b is discharged therefromvia conduit 8 a. The seawater discharged from each of chillers36,37,38,39 takes with it the heat absorbed from circulating water 23 fvia the refrigerant used in conjunction with each of the chiller'scondenser, evaporator and compressor. Once circulating water 23 f iscooled by chillers 36,37,38,39, the water (designated by referencenumeral 23 a) is circulated by the action of circulation pump 24 to thevessel's air handlers 42 where heat from the air in the respectivecompartments of the vessel is absorbed by the circulating water. Thereturning heated circulation water 23 b is then rerouted back to pump 24where it is then pumped to chillers 36,37,38,39 for cooling once again.

As the air temperature of the vessel begins to drop during the eveninghours and the heat load of the vessel gradually decreases, the chillersof the air conditioning system will begin to stage off one by one. Forexample, during the daytime, the climate air temperature may be 85° F.(or about 29.4° C.), thus requiring all of chillers 36,37,38,39 to beonline to cool and maintain the vessel compartments at an averagetemperature of 72° F. (or about 22.2° C.). When the climate airtemperature starts to decline during the evening hours, and assuming allof chillers 36, 37, 38, 39 are still on-line and in operation, thetemperature of circulating water 23 b returning from the vessel's airhandlers 42 will begin to drop. During this period of time lasting intothe night, chillers 39,38 and 37 will shut down one by one because itwill take less cooling of the circulation water 23 to maintain thevessel's compartments at a temperature of 72° F. (or about 22.2° C.).Eventually, when the temperature of the returning circulating water 23 breaches, for example, 52° F. (or about 11.1° C.), it will only benecessary to operate chiller 36 to maintain the prescribed airtemperature of the vessel compartments. It is during this time that theelectrical demand on generator 12 will be such that its diesel enginewill be operating under low-load conditions.

In order to maintain a sufficient electrical load on diesel enginegenerator 12 during these types of conditions, e.g., when only one ortwo of the chillers is in operation, load bank 16 is employed. Referringto FIG. 3 once again, when the temperature of the circulating water 23 breturning from the vessel's air handlers 42 reaches a predeterminedtemperature of, for example, 54° F. (or about 12.2° C.), temperaturesensing device 56 t will transmit a signal to corresponding thermostat56 that in turn transmits a signal to the electric motor (not shown) ofvalve 48 for opening the valve. The opened valve has the effect ofdiverting a portion of circulating water 23 c (which is under pressureby virtue of circulating pump 24) from circulation loop 28 throughconduit 28 b. If the temperature of returning circulating water 23 breaches a lower temperature of, for example 53° F. (or about 11.7° C.),then thermostat 57, which has been programmed to open valve 49 at thattemperature, will transmit an electrical signal from temperature sensingdevice 57 t to its corresponding electric motor (not shown) for openingvalve 49. This has the effect of admitting an increased portion ofcirculating water 23 c from conduit 28 a of circulation loop 28. Valves50 and 51 will open in a similar fashion when their correspondingtemperature sensing devices 58 t and 59 t detect a temperature of, forexample, 52° F. (or about 11.1° C.) and 51° F. (or about 10.6° C.),respectively, thereby diverting a greater portion of circulating water23 c from circulation loop 28.

Once diverted, the circulating water 23 c exiting any of valves48,49,50,51 is passed to load bank heat exchanger 46 via conduit 28 bwhere it is heat exchanged with, or in this case, absorbs the heat from,the heated seawater 21 b entering the heat exchanger from chillers36,37,38,39 via discharge conduit 8 a. Seawater 21 c, having transferredits heat to circulating water 23 c, exists heat exchanger 46 and isreturned back to the sea via conduit 8 b. As shown in FIG. 3, oncecirculating water 23 c is heated by seawater 21 b, the exitingcirculating water 23 d from heat exchanger 46 is returned to circulationloop 28 via conduit 28 c where it joins the remainder of circulationwater 23 b for entry into circulation pump 24 as circulating water 23 e.As a result, the temperature of the combined circulating waters 23 b and23 d as they leave pump 24, referenced by numeral 23 f, will beincreased to approximately 54° F. (or about 12.2° C.), thereby impartinga greater heat load on chiller 36. The added heat load carried bycirculating water 23 f will trigger the activation of chiller 37 toproduce a supply of chilled circulating water 23 a at a temperature of48° F. (or about 8.9° C.) for maintaining the 72° F. (or about 22.2° C.)air temperature demanded by the vessel compartments. The remainder ofchillers 38 and 39 will be activated in a similar fashion when thetemperature of circulating water 23 b drops to the predeterminedtemperature programmed into their corresponding thermostats 58 and 59.The activation of chillers 37,38 and/or 39 to cool the increased heatload carried by circulating water 23 f will therefore place a greaterelectrical load on generator 12, and as a result, will contribute tomaintaining a sufficient load on the diesel engine in order to avoid thedeleterious effects of low-load operation.

It will be understood that the temperature settings of the variousthermostats 56,57,58,59 can be set or varied to accommodate the heatload conditions in the vessel compartments and control the number ofchillers to be activated. For example, the settings for each ofthermostats 56,57,58,59 can be varied by increments of greater than onedegree to accommodate the capacity and operating parameters of chillers34,35,36,37. Moreover, in addition to setting the thermostats foractuating the chillers in stages, they can be programmed at the same orsimilar temperature settings so that two or more of the chillers can besimultaneously activated for coming on line. The load bank apparatusaccording to the invention therefore offers a wide degree of latitudefor controlling the operation of the chillers to create and maintain anelectrical load on diesel engine generator 12.

When circumstances warrant the heating of the vessel compartments, theair conditioning system 14 of system 10 will operate to supply heat tothe vessel compartments. For the purposes of the following example anddescription, it is assumed that heat transfers sources 36,37,38,39 arereverse-cycle chillers or heat pumps, or combinations thereof, both ofwhich will be collectively referred to as “heat pumps.” The operation ofa reverse-cycle chiller or heat pump is well known to those skilled inthe air conditioning industry and their brief description for heatingthe circulating water in a conventional closed-loop air conditioningsystem is presented under the “Background Of The Invention” heading setforth herein. Heat pumps 36,37,38,39 use the heat of seawater 21transported therethrough to heat the circulating water 23 in airconditioning system 14.

By way of example and for purposes of illustration, the heating demandfor the vessel will be the greatest during the evening hours, with allof the heat pumps 36,37,38,39 being online to maintain an averagetemperature in the vessel compartments at, for example, 75° F. (or about23.9° C.). The electrical power demand on generator 12 will therefore besufficient for maintaining an adequate load on its diesel engine. Duringthe early daytime hours, however, the climate air temperature willgradually increase and the heating demand for the vessel will besomewhat reduced. As the middle of the day is reached, the reverse cyclechillers will stage off one by one until only one heat pump 36 is neededto meet the heating demands of the vessel compartments. For example,when the temperature of circulating water 23 b increases to 130° F. (orabout 54.4° C.), it will be sensed by temperature sensing device 56 tand cause thermostat 56 to activate valve 48 into the open position,assuming a thermostat temperature setting of 130° F. (or about 54.4°C.). The opening of valve 48 will admit therethrough a portion ofcirculating water 23 c and allow transport of the same to heat exchanger46 via conduit 28 b where it is cooled by the chilled seawater 21 bexiting, for example, heat pump 36.

Once cooled, circulating water 23 d is returned to circulation loop 28where it is combined with circulating water 23 b for introduction topump 24 as circulating water 23 e. The chilled circulating water 23 fleaving pump 24 will have a temperature of approximately 120° F. (orabout 48.9° C.), which in turn will cause heat pump 37 to be activatedfor providing additional heat to circulating water 23 f, to maintainvessel compartments at the temperature requirement of 75° F. (or about23.9° C.). The activation of heat pump 37 will create an additionalelectrical demand on generator 12, thereby increasing the load on thediesel engine powering the same.

As the temperature of circulating water 23 b increases to sequentialtemperatures of, for example, 132° F. (or about 55.6° C.) and 134° F.(or about 56.7° C.), valves 38 and 39 will be activated, respectively,into the open position by their corresponding thermostats 58 and 59 toadmit therethrough additional amounts of circulating water 23 c forcooling by heat exchanger 46 with seawater 21 b. The additional loadcreated by the diversion and cooling of circulating water 23 c willcreate a corresponding demand on heat pumps 38 and 39 to provide asupply of heated circulating water 23 a to air handlers 42. As a result,a correspondingly greater electrical power demand will be placed ongenerator 12 as the activation of heat pumps 38 and 39 is initiated.

It will be appreciated that the effectiveness of heat pumps 36,37,38,39,whether they be reverse-cycle chillers or heat pumps, will, forpractical considerations, be economical and efficient only whenoperating in seawater temperatures above 48° F. (or about 8.9° C.). Therationale is that as the seawater temperature approaches freezingtemperatures, the seawater will be devoid of sufficient heat fortransference to circulating water 23. For this reason, it is moreeconomical and practical to use other or additional forms of apparatusfor heating the circulating water, either in conjunction with heat pumps36,37,38,39, or in lieu thereof. Therefore, as shown in FIG. 3, one ormore fluid heating devices in the form of, for example, electricalresistant fluid heating devices such as in-line resistant water heaters62,63,64 powered by diesel engine generator 12, are provided. The fluidheating devices are arranged in parallel relationship with respect toeach other in conduit 28 a of circulation loop 28. The advantage tousing in-line water heaters is that they offer an added economicalcapacity advantage due to their minimal space occupancy. When used inplace of heat pumps 36,37,38,39, the heat pumps are turned off. Whenused to complement heat pumps 36,37,38,39, the seawater discharge 21 bcontinues to heat exchange the circulating water 23 c via heat exchanger46 for maintaining the appropriate activation of heat pumps 36,37,38,39and heating devices 62,63,64. In this way, an electrical demand willcontinue to be placed on generator 12 under otherwise low-loadconditions. It will be appreciated that the use of fluid heating devicesother than heat pumps 36,37,38,39, such as electrical resistance waterheaters, are optional and are usually used in very cold climateconditions, for example when the seawater temperature is below about 48°F. (or about 8.9° C.)

Whether the air conditioning system 14 is used to cool or heat thevessel, circulating water 23 c can be heat exchanged with seawater froma source other than from the discharge of heat transfer sources 36,37,38and/or 39. As illustrated in FIG. 5 and as indicated hereinbefore,seawater 21 can be introduced from the sea to heat exchanger 46 byutilizing a separate conduit 8 c and seawater pump 27 for circulatingthe seawater (or any other functional fluid for the intended purpose)through the heat exchanger.

As an alternative to the use of load bank heat exchanger 46 in load bank16, one or more fluid heating devices other than chillers 36,37,38,39may be utilized when air conditioning system 14 is used to cool thevessel compartments. FIG. 4 illustrates such a system wherein allcomponents that are identical with or clearly analogous to thecorresponding part of the system shown in FIGS. 2, 3 and 5 are denotedby similar reference characters. Referring now to FIG. 4, and inaccordance with another embodiment of the invention, fluid heatingdevices in the form of electrical resistant fluid heating devices, suchas in-line electrical resistant water heaters 67,68,69,70, are providedin the return segment of circulation loop 28, the return segment beingthat section of circulation loop 28 in which the circulation water 23 bis returned from the vessel air handlers 42 back to chillers 36. In-lineresistant water heaters 67,68,69,70 comprise an electrically operatedcoil placed in the path of the circulating water 23 for heating the sameby supplying electrical power to the coil. Resistant water heaters67,68,69,70 are preferably placed at a point in the water circulationloop prior to the entry of circulating water 23 f to chillers36,37,38,39.

As indicated above, resistant water heaters 67,68,69,70 act as areplacement for electrically operated valves 56,57,58,59 and heatexchanger 46 for implementing the load bank according to the inventionherein. Each of resistant water heaters 67,68,69,70 are electricallycoupled with thermostats 56,57,58,59, respectively, within load bankcontroller 44, and being powered by diesel engine generator 12, act inconcert with chillers 36,37,38,39 to increase the electrical loadcapacity placed on the generator. Consistent with this aspect of theinvention, the load bank controller 44 comprises thermostats 56,57,58,59and their corresponding temperature sensing devices 56 t,57 t,58 t,59 t.As with the embodiment illustrated in FIG. 3, the temperature sensingdevices are disposed in circulating water 23 b, preferably at a point inthe circulation loop 28 where the circulating water 23 b exits thevessel's air handlers 42 prior to its entry to water circulation pump24.

In operation, when the temperature of the circulating water 23 breturning from the vessel's air handlers 42 reaches a predeterminedtemperature, for example, 56° F. (or about 13.3° C.), temperaturesensing device 56 t will transmit a signal to its correspondingthermostat 56 that in turn will transmit a signal to resistant waterheater 67 for activation of the same. Water heater 67, which alsoderives its power from diesel engine generator 12, will then heat thecirculating water 23 f entering the heater for return to any one or moreof chillers 36,37,38,39. The circulation water exiting resistant waterheaters 67,68,69,70 is identified as reference numeral 23 g in FIG. 4.Furthermore, if the temperature of returning circulating water 23 breaches a lower temperature of, for example, 54° F. (or about 12.2° C.),then the programming of thermostat 57, like thermostat 56, will activateresistant water heater 68 when that temperature is reached. This alsohas the effect of providing additional heat to the circulating water 23g entering the chillers. Resistant water heaters 69 and 70 will beactivated in similar fashion when their respective temperature sensingdevices 58 t and 59 t detect a temperature of, for example, 52° F. (orabout 11.1° C.) and 50° F. (or about 10.0° C.), thereby activatingchillers 38 and 39.

As with load bank 44 illustrated in FIG. 3, the combined effect ofincrementally heating circulating water 23 f based on the temperatureprogramming of thermostats 56,57,58,59, will place a proportionatelygreater heat load on any one or all of chillers 36,37,38,39 such thattheir activation will become necessary for maintaining an appropriatesupply of chilled water 23 a to air handlers 42. It will be appreciatedthat the demand for chilled circulating water 23 a in air conditioningsystem 14 is typically and ultimately dictated by the thermostaticdemand for cool air in the various compartments of the vessel. Theactivation of any or all of chillers 36,37,38,39 for maintaining thetemperature of the chilled circulating water 23 a entering air handlers42 will place a corresponding electrical power demand on generator 12which will have the effect of creating an increased load on the dieselengine to avoid no-load or low-load operation.

The advantage of using resistant water heaters 67,68,69,70 is that theypresent another source for creating an electrical power demand on dieselengine generator 12 above that created by the actuation of chillers36,37,38,39. For this reason, and in accordance with yet anotherembodiment of the invention, fluid heating means in the form of one ormore electrical resistant fluid heating devices, such as the in-lineelectrical resistant water heaters 67,68,69,70 illustrated in FIG. 4,may be added to the air conditioning system 14 illustrated in FIG. 3.The in-line water heaters (not shown in FIG. 3), which are powered bydiesel engine generator 12, may be situated anywhere in conduit 28 d ofcirculation loop 28, preferably between the circulating pump 24 andchillers 36,37,38,39, for adding heat to the circulating water 23 fprior to its entry to chillers 36,37,38,39. The operation of theseadditional in-line heaters may be undertaken independently of load bankcontroller 44. They may also be electrically connected with thermostats56,57,58,59 in the manner illustrated in FIG. 4 for their operation,either independently of valves 48,49,50,51, or in conjunction with them.

The system, apparatus and method according to the invention and variousembodiments described above, provides an inexpensive and economicalmeans by which the circulating heat transfer fluid in a closed loop airconditioning system can be utilized for creating a load bank on a marinediesel engine generator. In doing so, the systems, apparatus and methodsof the present invention dispense with the need for adding separate andspace consuming apparatus associated with conventional load banksystems, and avoids the prohibitive costs associated with theirinstallation and implementation onboard a marine vessel.

Since other modifications and changes may be varied to fit theparticular apparatus, operating requirements and environments of theinvention, which will be apparent to those skilled in the art, theinvention is not considered to be limited to the various aspects andembodiments chosen for purposes of disclosure, and covers all changesand modifications which do not constitute departures from the truespirit and scope thereof.

1. A system for maintaining an electrical load on a diesel enginegenerator for use on a marine vessel comprising: a) a closed-loop fluidair conditioning system for exchanging heat with the air in said vessel,comprising (i) first heat transfer means that receives therein anddischarges therefrom a first heat transfer fluid for ultimatelyexchanging heat with a second heat transfer fluid, said second heattransfer fluid being supplied to and returned from said vessel within aclosed circulation loop for exchanging heat with the air in said vessel;and b) a load bank comprising (i) controller means for diverting atleast a portion of the second heat transfer fluid being supplied to saidvessel, into heat exchange relationship with a third heat transferfluid; and (ii) second heat transfer means for exchanging heat betweensaid diverted second heat transfer fluid and said third heat transferfluid; whereby the diverted, heat-exchanged second heat transfer fluidis returned to said first heat transfer means for activation thereofthereby creating an electrical power demand on the diesel enginegenerator.
 2. The system according to claim 1 wherein the third heattransfer fluid is the first heat transfer fluid discharged from saidfirst heat transfer means.
 3. The system according to claim 2 whereinthe first heat transfer fluid comprises seawater.
 4. The systemaccording to claim 2 optionally comprising, in addition to said secondheat transfer means, a plurality of electrically operated resistantwater heaters arranged in parallel relationship relative to each other.5. The system according to claim 1 wherein the third heat transfer fluidcomprises seawater.
 6. The system according to claim 1 wherein saidsecondary heat transfer fluid comprises water, a mixture of ethyleneglycol and water, or a mixture of propylene glycol and water, the glycolcomponent being present in its respective mixture in an amount of fromabout 5 percent to about 25 percent, based on the total volume of themixture.
 7. The system according to claim 1 wherein the first heattransfer means comprises at least one chiller, reverse-cycle chiller orheat pump.
 8. The system according to claim 1 wherein the first heattransfer means comprises a plurality of chillers, reverse-cyclechillers, or heat pumps, or combinations thereof, arranged in parallelrelationship relative to each other.
 9. The system according to claim 1wherein said portion of second heat transfer fluid being supplied to thevessel is diverted in response to a predetermined temperature value ofthe returning second heat transfer fluid.
 10. The system according toclaim 1 wherein said controller means comprises at least one valve fordiverting said portion of said second heat transfer fluid being suppliedto the vessel.
 11. The system according to claim 10 wherein said valveis operably coupled with a thermostat, said valve being operated inresponse to a thermostat setting reflective of a predeterminedtemperature of the returning second heat transfer fluid.
 12. The systemaccording to claim 11 wherein said controller means comprises aplurality of valves and corresponding thermostats.
 13. The systemaccording to claim 12 wherein each valve is operably coupled with itscorresponding thermostat, each of said thermostats being in temperaturesensing relationship with the returning second heat transfer fluid, eachof said valves being operated in response to a signal generated by itscorresponding thermostat reflective of a predetermined temperature ofthe returning second heat transfer fluid detected upstream of itscorresponding valve.
 14. The system according to claim 1 wherein thesecond heat transfer means comprises a heat exchanger.
 15. The systemaccording to claim 14 wherein the heat exchanger is a plate type heatexchanger, a shell and tube type heat exchanger, or a tube and tube typeheat exchanger.
 16. The system according to claim 1 optionallycomprising, in addition to said second heat transfer means, one or moreelectrical resistant fluid heating devices in communication with thereturning second heat transfer fluid for heating the same.
 17. Thesystem according to claim 16 wherein said fluid heating device is aresistant water heater.
 18. A system for maintaining an electrical loadon a diesel engine generator for use on a marine vessel comprising: a) aclosed-loop chilled-fluid air conditioning system for cooling the air insaid vessel comprising: (i) at least one source of heat transfer thatreceives therein and discharges therefrom a first heat transfer fluidfor ultimately exchanging heat with a second heat transfer fluid, saidsecond heat transfer fluid being supplied to and returned from saidvessel within a closed circulation loop for cooling the air in saidvessel; and b) a load bank comprising (i) a controller for diverting atleast a portion of the second heat transfer fluid being supplied to saidvessel, into heat exchange relationship with a third heat transferfluid; and (ii) a heat exchanger for transferring heat from the thirdheat transfer fluid to the diverted portion of second heat transferfluid; whereby the heated, diverted second heat transfer fluid isreturned to said source of heat transfer for activation thereof tocreate an electrical power demand on the diesel engine generator formaintaining a load thereon.
 19. The system according to claim 18 whereinthe third heat transfer fluid is the first heat transfer fluiddischarged from said source of heat transfer.
 20. The system accordingto claim 19 wherein the first heat transfer fluid comprises seawater.21. The system according to claim 20 wherein the second heat transferfluid comprises water, a mixture of ethylene glycol and water, or amixture of propylene glycol and water, the glycol component beingpresent in its respective mixture in an amount of from about 5 percentto about 25 percent, based on the total volume of the mixture.
 22. Thesystem according to claim 21 wherein the air conditioning systemcomprises a plurality of chillers or reverse-cycle chillers, orcombinations thereof, arranged in parallel relationship relative to eachother.
 23. The system according to claim 22 wherein the controllercomprises a plurality of valves and corresponding thermostats, saidthermostats being in temperature sensing relationship with the returningsecond heat transfer fluid, and each of said valves being operated inresponse to a signal generated by its corresponding thermostatreflective of a predetermined temperature of the returning second heattransfer fluid detected upstream of its corresponding valve.
 24. Thesystem according to claim 18 wherein (a) the first heat transfer fluidcomprises seawater; (b) the second heat transfer fluid comprises water,a mixture of ethylene glycol and water, or a mixture of propylene glycoland water, the glycol component being present in its respective mixturein an amount of from about 5 percent to about 25 percent, based on thetotal volume of the mixture; and (c) the third heat transfer fluidcomprises seawater provided to said heat exchanger independently of saidsource of heat transfer.
 25. The system according to claim 18 whereinsaid source of heat transfer comprises a chiller or reverse-cyclechiller.
 26. The system according to claim 18 wherein the controllercomprises at least one valve for diverting said portion of said secondheat transfer fluid being supplied to the vessel.
 27. The systemaccording to claim 26 wherein said valve is operably coupled with athermostat, said valve being operated in response to a thermostatsetting reflective of a predetermined temperature of the returningsecond heat transfer fluid.
 28. The system according to claim 27 whereinthe controller comprises a plurality of valves and correspondingthermostats.
 29. The system according to claim 18 wherein the heatexchanger is a plate type heat exchanger, a shell and tube type heatexchanger, or a tube and tube type heat exchanger.
 30. The systemaccording to claim 18 optionally comprising, in addition to said heatexchanger, one or more electrical resistant fluid heating devices,powered by said diesel engine generator, in communication with thereturning second heat transfer fluid for transferring heat to the same.31. The system according to claim 30 wherein the fluid heating devicecomprises an electrically operated resistant water heater.
 32. A systemfor maintaining an electrical load on a diesel engine generator for useon a marine vessel comprising: a) a closed-loop chilled-fluid airconditioning system for cooling the air in said vessel comprising (i) atleast one source of heat transfer that receives therein and dischargestherefrom a first heat transfer fluid for ultimately exchanging heatwith a second heat transfer fluid, said second heat transfer fluid beingsupplied to and returned from said vessel within a closed circulationloop for cooling the air in said vessel; and b) a load bank comprising(i) fluid heating means comprising one or more electrical resistantfluid heating devices operably coupled with a controller means forheating the second heat transfer fluid returning from the vessel to saidsource of heat transfer in response to a predetermined temperature ofthe returning heat transfer fluid detected upstream of the fluid heatingmeans; whereby the heated second heat transfer fluid is returned to saidsource of heat transfer for activation thereof to create an electricalpower demand on the diesel engine generator for maintaining a loadthereon.
 33. The system according to claim 32 wherein the first heattransfer fluid comprises seawater and the second heat transfer fluidcomprises water, a mixture of ethylene glycol and water, or a mixture ofpropylene glycol and water, the glycol component being present in itsrespective mixture in an amount of from about 5 percent to about 25percent, based on the total volume of the mixture.
 34. The systemaccording to claim 33 wherein the source of heat transfer comprises aplurality of chillers or reverse-cycle chillers, or combinationsthereof, arranged in parallel relationship relative to each other. 35.The system according to claim 34 wherein said fluid heating meanscomprises a plurality of electrically operated resistant water heatersarranged in parallel relationship relative to each other and powered bysaid diesel engine generator.
 36. The system according to claim 34wherein said load bank comprises a plurality of electrically operatedresistant water heaters, arranged in parallel relationship relative toeach other, each water heater being powered by said diesel enginegenerator and operably coupled with and controlled by a correspondingthermostat in response to a thermostat setting reflective of apredetermined temperature of the returning second heat transfer fluiddetected upstream of its corresponding water heater.
 37. The systemaccording to claim 32 wherein the source of heat transfer comprise achiller or reverse-cycle chiller.
 38. The system according to claim 32wherein said fluid heating means comprises at least one electricallyoperated resistant water heater powered by said diesel engine generator.39. The system according to claim 32 wherein said controller meanscomprises at least one thermostat, said thermostat being in temperaturesensing relationship with the returning second heat transfer fluid. 40.A system for maintaining an electrical load on a diesel engine generatorfor use on a marine vessel comprising: a) a closed-loop fluid airconditioning system for heating the air in said vessel comprising: (i)at least one source of heat transfer that receives therein anddischarges therefrom a first heat transfer fluid for ultimatelyexchanging heat with a second heat transfer fluid, said second heattransfer fluid being supplied to and returned from said vessel within aclosed circulation loop for heating the air in said vessel; and b) aload bank comprising (i) a controller for diverting at least a portionof the second heat transfer fluid being supplied to said vessel, intoheat exchange relationship with a third heat transfer fluid; and (ii) aheat exchanger for transferring heat from the third heat transfer fluidto the diverted portion of second heat transfer fluid; whereby theheated, diverted second heat transfer fluid is returned to said sourceof heat transfer for activation thereof to create an electrical powerdemand on the diesel engine generator for maintaining a load thereon.41. The system according to claim 40 wherein the third heat transferfluid is the first heat transfer fluid discharged from said source ofheat transfer.
 42. The system according to claim 41 wherein the firstheat transfer fluid comprises seawater.
 43. The system according toclaim 42 wherein the second heat transfer fluid comprises water, amixture of ethylene glycol and water, or a mixture of propylene glycoland water, the glycol component being present in its respective mixturein an amount of from about 5 percent to about 25 percent, based on thetotal volume of the mixture.
 44. The system according to claim 43wherein the air conditioning system comprises a plurality ofreverse-cycle chillers or heat pumps, or combinations thereof, arrangedin parallel relationship relative to each other.
 45. The systemaccording to claim 44 wherein the controller comprises a plurality ofvalves and corresponding thermostats, said thermostats being intemperature sensing relationship with the returning second heat transferfluid, and each of said valves being operated in response to a signalgenerated by its corresponding thermostat reflective of a predeterminedtemperature of the returning second heat transfer fluid detectedupstream of its corresponding valve.
 46. The system according to claim40 wherein (a) the first heat transfer fluid comprises seawater; (b) thesecond heat transfer fluid comprises water, a mixture of ethylene glycoland water, or a mixture of propylene glycol and water, the glycolcomponent being present in its respective mixture in an amount of fromabout 5 percent to about 25 percent, based on the total volume of themixture; and (c) the third heat transfer fluid comprises seawaterprovided to said heat exchanger independently of said source of heattransfer.
 47. The system according to claim 40 wherein said source ofheat transfer comprises a reverse-cycle chiller or heat pump.
 48. Thesystem according to claim 40 wherein the controller comprises at leastone valve for diverting said portion of said second heat transfer fluidbeing supplied to the vessel.
 49. The system according to claim 48wherein said valve is operably coupled with a thermostat, said valvebeing operated in response to a thermostat setting reflective of apredetermined temperature of the returning second heat transfer fluid.50. The system according to claim 49 wherein the controller comprises aplurality of valves and corresponding thermostats.
 51. The systemaccording to claim 40 wherein the heat exchanger is a plate type heatexchanger, a shell and tube type heat exchanger, or a tube and tube typeheat exchanger.
 52. The system according to claim 40 optionallycomprising, in addition to said source of heat transfer, one or moreelectrical resistant fluid heating devices, powered by said dieselengine generator, in communication with the second heat transfer fluidbeing supplied to the vessel for heating the same.
 53. The systemaccording to claim 52 wherein the fluid heating device comprises anelectrically operated resistant water heater.
 54. A load bank for amarine diesel engine generator electrically coupled with a source ofheat transfer in a closed-loop fluid air conditioning system thatreceives and discharges a primary heat transfer fluid for ultimatelyexchanging heat with a secondary heat transfer fluid, the secondary heattransfer fluid being supplied to and returned from the compartments of amarine vessel within a closed circulation loop for exchanging heat withthe air in the vessel compartments, comprising: (a) controller means fordiverting at least a portion of the secondary heat transfer fluid supplyinto heat exchange relationship with a tertiary heat transfer fluid; and(b) a heat exchanger for exchanging heat between the diverted secondaryheat transfer fluid and the tertiary heat transfer fluid; whereby thediverted, heat-exchanged, secondary heat transfer fluid is returned tosaid source of heat transfer for activation thereof to create anelectrical power demand on the diesel engine generator for maintaining aload thereon.
 55. The load bank according to claim 54 wherein theprimary heat transfer fluid and tertiary heat transfer fluid isseawater.
 56. The load bank according to claim 55 wherein the tertiaryheat transfer fluid is the seawater discharged from said source of heattransfer.
 57. The system according to claim 55 wherein said secondaryheat transfer fluid comprises water, a mixture of ethylene glycol andwater, or a mixture of propylene glycol and water, the glycol componentbeing present in its respective mixture in an amount of from about 5percent to about 25 percent, based on the total volume of the mixture.58. The load bank according to claim 54 wherein the controller meanscomprises at least one valve.
 59. The load bank according to claim 58wherein said valve is operably coupled with a thermostat that is intemperature sensing relationship with the returning secondary heattransfer fluid from said vessel, said valve being operated in responseto a signal generated by said thermostat reflective of a predeterminedtemperature of the returning secondary heat transfer fluid detectedupstream of said valve.
 60. The load bank according to claim 59 whereinthe controller means comprises a plurality of valves and correspondingthermostats, said valves being arranged in parallel relationshiprelative to each other.
 61. The load bank according to claim 54 whereinthe heat exchanger is a plate type heat exchanger, a shell and tube typeheat exchanger or a tube and tube type heat exchanger.
 62. A method formaintaining a load on a diesel engine generator onboard a marine vesselutilizing the circulating heat transfer fluid contained within theclosed circulation loop of a fluid air conditioning system to exchangeheat with the air in said vessel, comprising: (a) transporting a primaryheat transfer fluid through a first heat transfer means of the closedcirculation loop fluid air conditioning system for ultimately exchangingheat with the circulating heat transfer fluid; (b) supplying andreturning the circulating heat transfer fluid in the closed circulationloop to and from the vessel, respectively, for heat exchange with theair therein; (c) diverting at least a portion of the circulating heattransfer fluid being supplied to the vessel, into heat exchangerelationship with a tertiary heat transfer fluid; and (d) returning thediverted, heat-exchanged circulating heat transfer fluid to said firstheat transfer means whereby said first heat transfer means is activatedto create an electrical power demand on the diesel engine generator formaintaining a load thereon.
 63. The method according to claim 62 whereinthe first heat transfer means comprises a chiller, a reverse-cyclechiller or a heat pump.
 64. The method according to claim 62 wherein thefirst heat transfer means comprises a plurality of chillers, areverse-cycle chillers or heat pumps, or combinations thereof, arrangedin parallel relationship relative to each other.
 65. The methodaccording to claim 62 wherein the heat exchange of the diverted portionof circulating heat transfer fluid and primary heat transfer fluid isundertaken by a second heat transfer means comprising a heat exchanger.66. The method according to claim 65 wherein the portion of circulatingheat transfer fluid being supplied to the vessel is diverted in responseto a predetermined temperature value of the returning primary heattransfer fluid.
 67. The method according to claim 66 wherein the portionof circulating heat transfer fluid is diverted by a controller meanscomprising at least one valve.
 68. The method according to claim 67wherein said valve is operably coupled with a thermostat that is intemperature sensing relationship with the returning circulating heattransfer fluid, said valve being operated in response to a thermostatsetting reflective of the temperature of the returning circulating heattransfer fluid detected upstream of said valve.
 69. The method accordingto claim 66 wherein the controller means comprises a plurality of valvesand corresponding thermostats.
 70. The method according to claim 65wherein the heat exchanger is a plate type heat exchanger, a shell andtube type heat exchanger, or a tube and tube type heat exchanger. 71.The method according to claim 62 wherein the primary heat transfer fluidcomprises seawater.
 72. The method according to claim 71 wherein thetertiary heat transfer fluid comprises seawater.
 73. The methodaccording to claim 71 wherein the tertiary heat transfer fluid comprisesthe seawater discharged from said first heat transfer means.
 74. Themethod according to claim 62 wherein the circulating heat transfer fluidcomprises water, a mixture of ethylene glycol and water, or a mixture ofpropylene glycol and water, the glycol component being present in itsrespective mixture in an amount of from about 5 percent to about 25percent, based on the total volume of the mixture.
 75. A method formaintaining a load on a diesel engine generator onboard a marine vesselutilizing the circulating heat transfer fluid contained within theclosed circulation loop of a chilled fluid air conditioning system thatincludes at least one chiller or reverse-cycle chiller, comprising: (a)supplying and returning the heat transfer fluid in the closedcirculation loop to and from the vessel, respectively, for cooling theair therein; (b) heating the heat transfer fluid returning from thevessel to said chiller or reverse-cycle chiller; and (c) returning theheated heat transfer fluid to the chiller or reverse-cycle chiller foractivating the same to create an electrical power demand on the dieselengine generator for maintaining a load thereon.
 76. The methodaccording to claim 75 wherein the heat transfer fluid is heated with atleast one electrical resistant fluid heating device.
 77. The methodaccording to claim 76 wherein said fluid heating device comprises anelectrically operated resistant water heater.
 78. The method accordingto claim 76 wherein said resistant fluid heating device is operated inresponse to a predetermined temperature value of the returning heattransfer fluid.
 79. The method according to claim 78 wherein theoperation of said fluid heating device is controlled by a thermostat,said thermostat being in temperature sensing relationship with thereturning heat transfer fluid upstream of said fluid heating device. 80.The method according to claim 75 wherein the returning heat transferfluid is heated by a plurality of resistant water heaters, each waterheater being operably controlled by a corresponding thermostat inresponse to a thermostat setting reflective of a predeterminedtemperature of the returning heat transfer fluid detected upstream ofsaid resistant water heaters.
 81. The method according to claim 75wherein the heat transfer fluid comprises water, a mixture of ethyleneglycol and water, or a mixture of propylene glycol and water, the glycolcomponent being present in its respective mixture in an amount of fromabout 5 percent to about 25 percent, based on the total volume of themixture.
 82. A system for maintaining an electrical load on a dieselengine generator for use on a marine vessel comprising: (a) aclosed-loop fluid air conditioning system for heating the air in saidvessel comprising: (i) a fluid heating means, powered by said dieselengine generator, comprising at least one electrical resistant fluidheating device for heating a first heat transfer fluid being supplied toand returned from said vessel within a closed circulation loop forheating the air in said vessel; and (b) a load bank comprising (i)controller means for diverting at least a portion of the first heattransfer fluid being supplied to said vessel, into heat exchangerelationship with a second heat transfer fluid; and (ii) a heatexchanger for exchanging heat between the second heat transfer fluid andthe diverted portion of the first heat transfer fluid; whereby theheat-exchanged, diverted first heat transfer fluid is returned to saidfluid heating means for activation thereof to create an electrical powerdemand on the diesel engine generator for maintaining a load thereon.83. The system according to claim 82 wherein said first heat transferfluid comprises water, a mixture of ethylene glycol and water, or amixture of propylene glycol and water, said glycols being present intheir respective mixtures in an amount of from about 5 percent to about25 percent, based on the total volume of the mixture.
 84. The systemaccording to claim 83 wherein said fluid heating means comprises aplurality of electrically operated resistant water heaters arranged inparallel relationship relative to each other.
 85. The system accordingto claim 83 wherein the second heat transfer fluid comprises seawater.86. The system according to claim 82 wherein said fluid heating meanscomprises an electrically operated resistant water heater.
 87. Thesystem according to claim 82 wherein said controller means comprises atleast one valve for diverting said portion of said heat transfer fluidbeing supplied to the vessel.
 88. The system according to claim 87wherein said valve is operably coupled with a thermostat, said valvebeing operated in response to a thermostat setting reflective of apredetermined temperature of the returning first heat transfer fluid.89. The system according to claim 82 wherein said controller meanscomprises a plurality of valves and corresponding thermostats.
 90. Thesystem according to claim 89 wherein each valve is operably coupled withits corresponding thermostat, each of said thermostats being intemperature sensing relationship with the returning first heat transferfluid upstream of its corresponding valve, each of said valves beingoperated in response to a signal generated by its correspondingthermostat reflective of a predetermined temperature of the returningfirst heat transfer fluid.
 91. The system according to claim 82 whereinthe heat exchanger is a plate type heat exchanger, a shell and tube typeheat exchanger or a tube and tube type heat exchanger.